Switch to indirect references rather than direct pointers.

This also required a bit of fiddling to break cyclic dependencies,
now "jni_internal.h" needs Mutex from "thread.h".

Change-Id: I1d6fb2d801c190f72255f5e447a0a8a65cc3e673
diff --git a/src/indirect_reference_table.cc b/src/indirect_reference_table.cc
index 20f39b6..b30ce53 100644
--- a/src/indirect_reference_table.cc
+++ b/src/indirect_reference_table.cc
@@ -269,7 +269,7 @@
       segmentState.parts.topIndex = topIndex;
     } else {
       segmentState.parts.topIndex = topIndex-1;
-      LOG(INFO) << "+++ ate last entry " << topIndex-1;
+      //LOG(INFO) << "+++ ate last entry " << topIndex-1;
     }
   } else {
     /*